The present invention relates to cellular communications systems and, in particular, to a multiple hyperband cellular communications system and multiple hyperband capable mobile stations for operation therein.
North American cellular communications have historically been implemented solely in the 800 MHz Cellular hyperband. The most recent evolution in cellular communications services involves the adoption of three additional hyperbands for use in handling mobile communications. Of these additional hyperbands, only the Personal Communication Services (PCS) hyperband in the 1900 MHz frequency range has been completely defined. With the existence of the new PCS hyperband, different types of subscriptions and or services like speech quality, voice privacy, and encryption may exist for one mobile station from one hyperband to another, or from one frequency band in the Cellular hyperband to another frequency band in the PCS hyperband.
The Cellular hyperband is assigned two telephone frequency bands (commonly referred to as the A frequency band and the B frequency band) for carrying and controlling communications. The PCS hyperband, on the other hand, is specified in the United States of America to include six different frequency bands (A, B, C, D, E and F). Thus, in accordance with EIA/TIA Interim Standard IS-136 (the "IS-136 specification") as modified by the PN3388-1 specification version of Sep. 9, 1994 project no. 3011-1, eight frequency bands are now available in any given service area to facilitate communications services.
Each one of frequency bands specified for the Cellular and PCS hyperbands is allocated a plurality of voice or speech channels and at least one access or control channel. The control channel is used to control or supervise the operation of mobile stations by means of information transmitted to and received from the mobile stations. Such information may include incoming call signals, outgoing call signals, page signals, page response signals, location registration signals, voice channel assignments, maintenance instructions, hand-off, and cell selection or reselection instructions as a mobile station travels out of the radio coverage of one cell and into the radio coverage of another cell. The control or voice channels may operate in either an analog mode, a digital mode, or a combination mode.
The individual frequency bands are typically assigned to, and provided within a hyperband for the service area by only one service company. For example, the A frequency band of the Cellular hyperband is usually reserved for use by non-wire line communications service companies, and the B frequency band is usually reserved for use by wire line communications service companies. In some instances, a frequency band assigned to one service company for a given cell or service area may be assigned to a different service company in another cell or service area. It is also recognized that the same service company may provide cellular communications service in multiple frequency bands within either a single hyperband or across multiple hyperbands.
Cellular hyperband mobile stations have historically been configured to operate in a particular one of the available frequency bands within the Cellular hyperband. For example, if the service company providing cellular service to the subscriber is a wire line company, the Cellular hyperband mobile station is configured with the B frequency band as its "home" frequency band. Reciprocal billing arrangements between service companies allow subscribers to place calls over non-home frequency bands in the event the mobile station is roaming. These non-home calls, however, typically require payment by the subscriber of some form of a surcharge and are therefore undesirable. Furthermore, in the absence of an agreement between service companies, roaming subscribers may not be able to make a call without operator assistance. For the service provider, use of foreign frequency bands by subscribers results in a potential loss of revenue that the provider would like to avoid.
The expansion to multiple hyperband communications capabilities as a result of the IS-136 specification has necessitated the development and placement into service of mobile stations that are capable of accessing both the Cellular and PCS hyperbands. Furthermore, the existence of multiple available hyperbands for carrying mobile station communications presents an opportunity for cellular telephone switches to control overlapping or adjacent cells in different hyperbands. It would be beneficial if the cellular communications system were configured from both the system and terminal point of view to allow multiple hyperband capable mobile stations to operate seamlessly between the available hyperbands. At the same time, however, existing mobile units which are capable of operation only in the Cellular hyperband should enjoy continued support.